Conducting polymers have been used to modify electrode surfaces and to immobilize enzymes to construct biosensors for the detection of biomedically important species such as nitric oxide(NO), glucose, histamine, etc. We will use other substrates such as nanomaterials including nanotubes and nanoparticles, silica solgel, surfactants, and self-assembled monolayers (SAMs) to modify electrode surfaces for the immobilization of biomolecules in order to develop sensors for biomedically important species such as NO, thiols, histamine, and calcium. During the current grant period we have successfully measured the formal potentials of myoglobin and cytochromes by direct electrochemistry at electrodes modified with those substrates. We will use this approach to study several novel proteins such as pirin, decarboxylase enzymes, and diheme proteins by collaborating with two biochemistry professors at the University of Mississippi Medical Center. The hypotheses for the study are as follows:(1) the electrodes modified with those substrates help to carry out direct electrochemistry of novel proteins, and (2) the novel proteins on (or in) those substrates maintain the native form or at least these proteins are not denatured. Electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) will be used to determine the formal potentials of those proteins on (or in) different substrates. Electrochemistry will also be used to probe the interaction of the metal center (e.g., Fe) with dioxygen, NO, and the related transcriptional cofactors such as P50. These studies will help to find protein/matrix systems which may provide a fast electron transfer rate between the protein molecule and the substrate for the development of more sensitive transducers. These electrochemical studies will also provide valuable information for the protein chemistry involved in biomedical research. Those protein molecules on the modified electrodes as well as in solutions will also be characterized by spectroscopic methods including laser-Raman, FT-IR, UV-vis, atomic force microscopy (AFM), TEM, and SEM. These studies will provide spectroscopic evidence for the interactions between enzyme proteins and the modified electrodes and may be able to explain the differences.in electrochemical behaviors of protein molecules on different substrates.